In nonferrous refining, different kinds of refining intermediates occur and raw materials of various forms exist. Although these refining intermediates and raw materials contain valuable metals, they also include arsenic and other environmentally undesirable elements. A method for removing arsenic has been developed that involves combining arsenious acid with iron, calcium or the like and capturing the arsenic present in the solution in the arsenic compound. The arsenic compound is precipitated out and needs to be separated and removed by filtering. The filterability at this time varies greatly with the state of the arsenic compound. When the arsenic compound is gel-like, the filterability is very poor and processing on an industrial scale is difficult. In other words, the state of the produced arsenic compound is a critical factor influencing the productivity of the arsenic removal processing.
The precipitated and removed arsenic compound is either stored or disposed of, and it is important to minimize the amount of arsenic that elutes back out of the compound. Scorodite (FeAsO4.2H2O) is known as a type of arsenic compound with a low amount of arsenic elution. A marked improvement in arsenic removal processing can therefore be expected if scorodite suitable for filtering is formed. However, industrially generated arsenic-containing solutions contain valuable metals and other elements in a multiplicity of forms. No technology has yet been established for forming scorodite from solutions of this type.
Related prior art can be found in JP Sho-54-160590A.